Environmental groups are calling for the postponement of TransTasman Resources' application to mine ironsands in the Exclusive Economic Zone off the coast from Patea, claiming the company has not taken all relevant considerations into account.

While the five member panel of commissioners considering the application declined to adjourn the hearings, which are scheduled to take around two months, they did call for legal advice on whether TTR might also need a resource consent under the Resource Management Act, as well as an EEZ Act marine consent.

That followed submissions by the Environmental Defence Society that if sediment released in the mining process drifted inside the 12 mile nautical limit, TTR would require an RMA consent as well as a marine consent.

The area TTR proposes to mine is all outside the 12 mile limit, and is therefore governed only by the EEZ Act, but one of the major issues in the hearings will be the impact of sediment plumes on the surrounding environment when TTR returns sands that have been stripped of iron ore to the seafloor.

Iron ore comprises around 10 percent of the volume of the sands to be mined, with the remaining 90 percent to be returned to the seafloor, where impacts on the relatively sparse seafloor life in the area should recover within two to five years, according to TTR's submissions.

TTR had originally planned to mine an area straddling the 12 mile limit but chose instead to concentrate on a 66 square kilometre area between 22 kilometres and 36 kilometres from shore. Its opening submissions yesterday said the seabead in the relatively shallow waters of the South Taranaki Bight were already subject to regular, natural "perturbation".

The main thrust of submissions from both EDS and the lobby group Kiwis Against Seabed Mining (KASM) is that inadequate information and baseline scientific research meant consent should either be refused or approved only in stages, and using an adaptive management approach.

The EEZ Act required caution, and an adaptive management regime would mean the project could proceed only once each staged element had proven to work as well as claimed.

"Adaptive management should not be used as a way of finding out what the effects of an activity will be," the EDS submission. "In the event that consent is granted, the Environmental Protection Authority is able to grant a staged consent. This may include carefully defined thresholds or environmental indicators as preconditions to approval of subsequent stages."

It also challenged TTR's suggestion that a staged approach could threaten the project's economic viability

"It would be an error of law to state that a consent condition cannot be imposed requiring staging of this proposal on the assertion that this makes the project not viable to investors."

KASM's submission opposed the project on broad grounds, including negative impacts on the mining area, its surrounds and distant coastal marine environment, "changing the physical, chemical and biological nature of the seawater, causing ecosystem stress and reducing the ability for life in the water column and on the seabed to exist, thus degrading the quality of the oceans as a whole."

"Specific potential adverse effects identified in our expert evidence include on the marine biodiversity, including the benthos and marine mammals, including blue whales and Maui's dolphins."

TTR had "failed to sufficiently address the crucial, and in our submission, central, issue of the effects of the mining on the benthic environment. This, in our submission, is a fundamental and crippling failure."

It sought adjournment of the hearings while these alleged deficiencies were remedied, which the EPA-appointed commissioners declined, saying this could be dealt with during expert witness testimony later this month.